1. Field of the Invention
The present invention relates to organosilicate layers, their use in integrated circuit fabrication, and a method for forming an organosilicate layer.
2. Description of the Background Art
Integrated circuits have evolved into complex devices that can include millions of components (e. g., transistors, capacitors and resistors) on a single chip. The evolution of chip designs continually requires faster circuitry and greater circuit density. The demands for greater circuit density necessitate a reduction in the dimensions of the integrated circuit components.
As the dimensions of the integrated circuit components are reduced (e. g., sub-micron dimensions), the materials used to fabricate such components contribute to their electrical performance. For example, low resistivity metal interconnects (e. g., copper and aluminum) provide conductive paths between the components on integrated circuits. Typically, the metal interconnects are electrically isolated from each other by an insulating material. When the distance between adjacent metal interconnects and/or the thickness of the insulating material has sub-micron dimensions, capacitive coupling potentially occurs between such interconnects. Capacitive coupling between adjacent metal interconnects may cause cross talk and/or resistance-capacitance (RC) delay which degrades the overall performance of the integrated circuit. In order to prevent capacitive coupling between adjacent metal interconnects, low dielectric constant (low k) insulating materials (e. g., dielectric constants less than about 4.5) are needed.
The demands for greater integrated circuit densities also impose demands on the process sequences used for integrated circuit manufacture. For example, in process sequences using conventional lithographic techniques, a layer of energy sensitive resist is formed over a stack of material layers on a substrate. Many of these underlying material layers are reflective to ultraviolet light. Such reflections can distort the dimensions of features such as lines and vias that are formed in the energy sensitive resist material.
One technique proposed to minimize reflections from an underlying material layer uses an anti-reflective coating (ARC). The ARC is formed over the reflective material layer prior to resist patterning. The ARC suppresses the reflections off the underlying material layer during resist imaging, providing accurate pattern replication in the layer of energy sensitive resist.
Therefore, a need exists in the art for low dielectric constant materials suitable for integrated circuit fabrication. Particularly desirable would be a low dielectric constant material that is also an ARC.
A method for forming an organosilicate layer for use in integrated circuit fabrication is provided. In one embodiment, the organosilicate layer is formed by applying an electric field to a gas mixture comprising a phenyl-based silane compound. The gas mixture may optionally include an oxidizing gas.
The organosilicate layer is compatible with integrated circuit fabrication processes. In one integrated circuit fabrication process, the organosilicate layer is used as an antireflective coating (ARC) for DUV lithography. For such an embodiment, a preferred process sequence includes forming the organosilicate layer on a substrate. The organosilicate layer has a refractive index (n) in a range of about 1.20 to about 1.70 and an absorption coefficient (xcexa) in a range of about 0.1 to about 0.7 at wavelengths less than about 250 nm. The refractive index (n) and the absorption coefficient (xcexa) for the organosilicate layer are tunable, in that they can be varied in the desired range as a function of the deposition temperature as well as the gas composition used during layer formation. After the organosilicate layer is formed on the substrate, a layer of energy sensitive resist material is formed thereon. A pattern is defined in the energy sensitive resist at a wavelength less than about 250 nm. Thereafter, the pattern defined in the energy sensitive resist material is transferred into the organosilicate layer. After the organosilicate layer is patterned, such pattern is optionally transferred into the substrate using the organosilicate ARC layer as a hardmask.
In another integrated circuit fabrication process, the organosilicate layer is incorporated into a damascene structure. For such an embodiment, a preferred process sequence includes depositing a first dielectric layer on a substrate. An organosilicate layer is then formed on the first dielectric layer. Thereafter, the organosilicate layer is patterned and etched to define contacts/vias therethrough. After the organosilicate layer is patterned and etched, a second dielectric layer is deposited thereover. The second dielectric layer is then patterned and etched to define interconnects therethrough. The interconnects formed in the second dielectric layer are positioned over the contacts/vias formed in the organosilicate layer. After the interconnects are formed the contacts/vias defined in the organosilicate layer are etched through the first dielectric layer to the substrate surface. Thereafter, the damascene structure is completed by filling the interconnects and contacts/vias with a conductive material.